1. Field of the Invention
This invention relates to a pressure relief device that has a plug that is mounted within a plug cavity of a plug housing. When the plug moves within the cavity from a closed condition to an open condition of the pressure relief device, a bypass passage communicates with an inlet and an outlet of the plug housing and thereby allows the pressurized fluid to discharge.
2. Description of Prior Art
U.S. Pat. No. 1,744,977 discloses a temperature controlled relief valve. The valve has a tubular skirt portion with openings. The tubular skirt portion fits within a passageway to guide the valve in its movement between a seated position and a non-seated position. In the seated position, a fusible material is positioned to retain a plug which is rotatably mounted with respect to a valve body. The fusible material is positioned between a downstream face of a cylindrical stem and the plug. When the fusible material melts, the plug moves with respect to the valve body and thereby exposes openings for communication between an inlet and an outlet of the valve.
U.S. Pat. No. 1,924,417 teaches a valve that has a fusible material positioned between a downstream face of a valve stem and a cap member. As the fusible material melts, the valve stem forces the fusible material into an annular space and thus allows a valve seat to move and thereby form communication between an inlet and an outlet of a valve body.
U.S. Pat. No. 2,671,461 teaches a valve that operates with fusible material. A valve stem is urged into a normally closed position by a force applied to the fusible material which contacts the valve stem. When the fusible material melts, air pressure from an inlet side forces the stem into an open position and thus allows communication between an inlet and an outlet of the valve.
U.S. Pat. No. 3,618,627 discloses a pressure relief valve which has a fusible plug positioned in a valve stem. A spring urges a plunger into a normally closed position. As the fusible material melts and flows into spaces provided by the spring, the plunger moves into an open position and allows communication between an inlet and an outlet of the valve.
U.S. Pat. No. 5,275,194 discloses a fire control valve that has a replaceable locking pin assembly. A fusible material holds a locking pin in a locked position which retains a valve member in a closed position. As the fusible material melts, a spring-loaded locking pin forces the fusible material out of a housing and allows a valve member to move and thereby form communication between an inlet and an outlet of the valve. In a closed position of the valve, one site pin extends beyond a housing to indicate valve closure and in an open condition of the valve, another pin extends beyond the housing to indicate the open condition of the valve. Only one of the two pins are exposed or extend beyond the housing at one time.